Background and Objectives: Regardless of how many periods and how long the androgenic-anabolic steroids have been used, they can cause side effects. The objective of this study was to investigate the effect a 6-week endurance training and using different doses of anabolic steroid boldenone on hematological factors and changes in spleen structure in male Wistar rats.

Methods: In this experimental study, 47 male Wistar rats aged 12 weeks, were randomly divided into 7 groups (control, sham, boldenone-1, boldenone-2, endurance training, endurance training+boldenone-1, endurance training+boldenone-2). Increasing endurance training program was performed at the speed of 10-30m/min (Vo2max, 75-80%) for 6 weeks and 5 days/week. The drug was injected deeply into the quadriceps and hamstring muscles once a week, on an appointed day. After anesthesia and dissection, the spleen was removed. Finally, the selected microscopic sections, were studied using a light microscope after staining with hematoxylin and eosin. Data were analyzed by dependent t-, one-way ANOVA, and post-hoc LSD tests at α<0.05 level.

Results: In this study, boldenone supplementation at different doses led to weight gain, non-significant decrease in spleen weight (p=0.297), increase in white blood cells (p=0.041), and increase in hematocrit level (p=0.017). Also, there was a significant difference between the effect of exercise and boldenone consumption on the extent of damage to white pulp, red pulp, and the spleen sinusoidal space (p=0.001).

Conclusion: The findings of this study showed it is likely that short-term consumption of boldenone have negative effects on the spleen structure, followed by negative changes in hematological factors.